docs: def export(self, nidm_version, export_dir):
          """
          Create prov entities and activities.
          """
          # Create "Excursion set" entity
          self.add_attributes((
              (PROV['type'], self.type),
              (NIDM_IN_COORDINATE_SPACE, self.coord_space.id),
              (PROV['label'], self.label),
          ))
  
          if self.visu is not None:
              self.add_attributes((
                  (DC['description'], self.visu.id),
              ))
  
          if self.clust_map is not None:
              self.add_attributes((
                  (NIDM_HAS_CLUSTER_LABELS_MAP, self.clust_map.id),
              ))
  
          if self.mip is not None:
              self.add_attributes((
                  (NIDM_HAS_MAXIMUM_INTENSITY_PROJECTION, self.mip.id),
              ))
  
          if self.num_clusters is not None:
              self.add_attributes((
                  (NIDM_NUMBER_OF_CLUSTERS, self.num_clusters),
              ))
  
          if self.p_value is not None:
              self.add_attributes((
                  (NIDM_P_VALUE, self.p_value),
              ))